Process for the heat-treatment of carbon-containing feed stock



2 Shets-Sheet 2 I E. G. BAILEY PROCESS FOR THE HEAT TREATMENT OF CARBON-CONTAINING FEED STOCK Aug. 22, 1950 Filed larch 23, 1944 INVENTOR Era in Baile Patented Aug. 22, 1950 PROCESS FOR THE HEAT-TREATMENT OF CARBON -CONTAINING FEED STOCK Ervin G. Bailey, Easton, Pa., assignor to The Babcock & Wilcox Company, Rockleigh, N. J a corporation of New Jersey Application March 23, 1944, Serial No. 527,726

8 Claims. (01. 48-197) The present invention relates to a process of and apparatus for the treatment of hydrocarbons and carbohydrates with heat, oxygen and steam to produce fuel gas of moderate heating value and also condensable hydrocarbons and other end products of a more valuable nature.

Gas producers heretofore available in which gaseous end products are produced by the reaction of air and steam with a body of hydrocarbon, usually in the form of a mass of solid fuel, such as bituminous coal, have been characterized by diflicult and ineflicient operation and the production of relatively low grade fuel gas and by-products (mainly troublesome tars) of little commercial value. The conversion of a solid fuel, such as raw bituminous coal, into such end products in a gas producer causes the volatile constituents of the fuel to be distilled under conditions adverse to the formation of valuable hydrocarbon compounds. Under the action of heat the coal melts or fuses into a state of relatively high viscosity and the presence of a melted tarry mass of coal in the producer bed tends to fill the voids in the fuelbed and preclude the free flow and distribution of the combustion air and steam supplied with the result that the combustible gases produced are of relatively low quality even with continual mechanical stoking and other troublesome operating procedures.

In accordance with the present invention, hydrocarbon and carbohydrate materials, preferably in a solid state, although such materials in a liquid or gaseous state may also be used as prime or supplemental feed stock, are subjected to a thermal decomposition or pyrolysis process in which the gasifiable constituents of the material being treated are continuously and completely gasified under controlled time and temperature conditions to bring about reactions which yield the maximum value of the combination of non-condensable gaseous end products and condensable end products suitable for further treatment to produce hydrocarbons suitable for motor fuels, aromatic hydrocarbons and other valuable products.

In operating the present process the hydrocarbon or carbohydrate feed stock to be treated is continuously supplied to the upper part of a vertically elongated retort through which is substantially continuously movingdownwardly a fluent mass of solid heat transfer material capable of being heated in different zones to a wide range of temperatures, and substantially continuously discharged from the bottom of the retort and returned to the upper part thereof by suitable external elevator or lifting provisions. The feed stock is introduced into the top of the retort chamber intermingled with pieces of heat transfer material at a sufficiently elevated temperature, e. g. 500-1000 F., and with a volumetric ratio of feed stock to heat transfer material sufliciently small, so that as the feed stock is heated by conduction and radiation from the hot heat transfer material to drive out any moisture present and leave the feed stock in a highly viscous condition, the feed stock will adhere to the pieces of heat transfer material but will not be in suflicient volume to completely fill the voids therebetween nor to congeal into an impervious mass which would otherwise prevent the heat transfer material and feed stock from passing downwardly in the retort chamber as a fluent mass or of gases flowing through the fluent mass in intimate contact with all portions thereof. The gases and condensable vapors driven oif in this low temperature gasiflcation zone flow through the interstices in the fluent mass and are continuously discharged from the retort at a predeterminedelevation, depending upon the desired end products of the process.

The described low temperature heating continues for a time interval sufficient to convert the feed stock in the descending fluent mass into so-called low-temperature coke or char, which normally still contains some hydrocarbons, and in this condition the feed stock enters the lower or high temperature section of the retort chamber, from the upper part of which section all of the gaseous products produced therein can be withdrawn. The upper part of the lower section serves as a high temperature gasification zone, in which the residence time of the feed stock and the high temperatures to which it is subjected are such that desirable hydrocarbons are formed by further distillation of the feed stock and pyrolysis and synthesis of the various compounds and elements normally present in this sectio In the lower part of the gasification zone, the descending high temperature fluent mass of coke or char and heat transfer material is contacted by superheated steam at a relatively high temperature and a water gas reaction takes place between some of the carbon and steam, forming hydrogen and carbon monoxide, which flow upwardly in the retort chamber and mix with the hydrocarbons produced in the upper part of the lower gasiflcation zone.

The residual carbon remaining on or intermingled -with the heat transfer material after passing through the water gas reaction zone serves as the source of heat, when burned, for effecting the water gas and pyrolysis reactions in the higher sections of the retort chamber. For this purpose oxygen, either in the form of commercially pure oxygen or air, or a mixture of air and oxygen, is introduced into the lowermost part of the retort chamber along with or below the elevation at which the steam is introduced, for combustion of the residual carbon. The portion of the feed stock consumed, and amount of combustion air introduced, for combustion purposes is regulated in accordance with the desired temperatures in the different sections of the retort. The heating gases generated by the complete and/or partial combustion of the residual carbon flow upwardly through apparatus and process of gasiflcation which is characterized by the continuous production of high quality condensable and non-condensable end products, high capacity operation and complete utilization of the volatile and gasifiable constituents of the hydrocarbon or carbohyrate the interstices in the descending mass of heat transfer material and feed stock, and mixed with the other gases and vapors produced in the lower zone, are advantageously withdrawn from the upper part of that zone. The amount of carbon dioxide in the heating gases is substantially reduced by the high temperature reducing action thereon of the descending residual carbon to form carbon monoxide. The presence of substantial amounts of hydrogen and carbon monoxide at high temperatures and with a sufficient residence time in the upper part of the lower z'one in.intimate contact with the descending coke or char residue and gaseous hydrocarbons driven oil is conducive to the formation therein of hydrocarbons of a more valuable composition. Other desirable hydrocarbon compounds may be formed by mixing the low temperature volatile gases distilled in the upper zone of the retort with the gaseous products in the high temperature gasification zone and withdrawing all or substantially all of the gases at an elevation near the mid-height of the retort. Alternately, the low temperature volatiles may be withdrawn from the retort chamber separately or with only a small portion of the gaseous hydrocarbons from the high temperature zone.

The descending heat transfer material on leaving the combustion zone is at a high temperature and the heat content thereof is partly utilized to preheat the incoming air and, steam flowing to the combustion and gasification zones, and partly to provide sufficient heat therein for the distillation of the low temperature volatiles in the gasifia'ble feed stock entering the upper distillation zone, to which the heated heat transfer material is returned. The described process and apparatus are applicable to the gasificaticn of a wide range of hydrocarbon and carbohydrate materials such as coal, lignite, peat, hogged wood, sawdust, bunker C or other heavy oil, oil shale, and mixtures of such materials.

The general object of the invention is thus the provision of an improved process and apparatus for continuously heat treating hydrocarbon and carbohydrate materials, in solid, liquid or gaseous form, under controlled reaction time and temperature conditions to produce condensable and non-condensable gaseous end products of greater commercial value than the material treated. Another object is the provision of a gasification process and apparatus in which the chemical compositions of the end products can be readily controlled over a relatively wide range by varying the reaction times and temperatures to which various constituents of the hydrocarbon or carbohydrate feed stock are subjected while undergoing treatment. A further and more specific object is the provision of a gas producing feed stock.

The various features of novelty which characterlze my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific Objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described. a preferred embodiment of my invention.

In the drawings:

Fig. 1 is an elevation, partly broken away and diagrammatic, of a retort and associated apparatus for carrying out the process of the invention;

'Fig. 2 is a sectional elevation of the retort shown in Fig. 1;

Fig. 3 is a horizontal section taken on the line 3-4 of Fig. 2;

Fig. 4-is a vertical section taken on the line 4-4 of Fig. 3; and

Fig.5 is a horizontal section 5-5 of Fig. 2.

The apparatus illustrated is particularly designed for the gasificationof crushed or coarsely pulverized solid hydrocarbons, such as a high volatile bituminous coal, and as shown comprises as its main elements a vertically elongated retort III, a fluid sealing material discharge mechanism ll receiving material from the lower end of the retort, elevating mechanism l2 receiving taken on the line material from the discharge mechanism I l and returning the same to the upper end of the re tort, and provisions I3 for supplying feed stock to the upper end of the retort.

As shown in Figs. 2 and 3, the retort In is formed by a fluid-tight cylindrical steel casing I5 lined with suitable refractory material Is to form a vertically elongated retort chamber I! of upwardly tapering circular cross-section. The upper end of the retort chamber has a refractory lined top plate I 8 provided with a normally closed central access opening 19, through which an inlet pipe 20 extends downwardly into the upper end of the retort chamber. The pipe 20 is connected to the feed stock supply system and has a branch pipe 22 leading from the elevating mechanism l2. The lower end of the retort chamber is formed by an inverted frusto-conical metallic plate 24 having a central discharge opening 25 at its lower end and perforated over the -major portion of its height. The plate 24 forms the inner wall of a downwardly tapering annular inlet chamber 26, the outer wall of which is a second inverted frusto-conical plate 21 also terminating in a central discharge opening 28 below and in axial alignment with the discharge opening 25.

A fluid inlet pipe 30 opens horizontally into one side of the inlet chamber 26. The pipe 30 is connected to a forced draft fan 33, as shown in Fig. 1, with the air supply therefrom controlled by a valve 34 in the pipe 30. A valve controlled steam supply pipe 32 extends into the pipe 30 and terminates therein adjacent its entrance to the inlet chamber 28 for mixing purposes. The operation of the fan 33 permits the air flow to be controlled independently of the steam flow.

As shown in Figs. 2 and 5, a supplementary or alternative steam supply is provided by a spider 29. having connected concentric inner and outer perforated rings in the lower part of the chamber I1. The outer ring of the spider-is connected by vertical pipes 3| to an extemal valve controlled trol the volumetric ratio of feed stock to heat transfer materialentering the inlet pipe 20 and each of which sets is formed, as shown in Figs.

'jectlng pipes 4|. The outlet pipes 4| are separately connected to a subjacent common annular bustle pipe 42 by downwardl extending discharge pipes 42. A discharge line 43 controlled by a valve 44 connects the upper bustle pipe to a storage point or associated apparatus, and a second discharge line 45 controlled by a valve 46 is similarly connected to the lower bustle pipe. A suitable gas quenching nozzle 48 is arranged to discharge into the upper end of each discharge pipe 42 in intimate contact with .the gases discharging therethrough.

In operation the retort chamber i1 is filled to approximately the level indicated in Fig. 2 with a fluent mass ofmaterial, a substantially contlnuous downward movement of which is effected without change in level by the substantially continuous introduction of material through the inlet pipe 20 and its discharge through the discharge openings 25 and 28. The discharge outlet 28 opens into a vertical discharge pipe 49,

which is connected through an expansion joint 50 to an inclined pipe 5|. The fluid sealing material discharge mechanism I I is incorporated in the pipe-49 and as shown consists of a variable speed rotary pocket feeder 52 driven by an electric motor 53 through suitable speed reducing devices 54. The lower end of the pipe 5! opens into a box 55 having openings therein for the addition and withdrawal of circulating material. From the box 55, the circulated material drops into the elevator casing 51 of the elevating mechanism I2. The elevator casing is of welded gastight construction and encloses an elevator driven by an electric motor 6!. The elevator buckets empty into a discharge pipe 62 having a bottom outlet opening into an inclined pipe 63, which is connected to the upper end of the branch inlet pipe 22 through an expansion joint 64. With this arrangement a substantially continuous circulation of material can be maintained externally of the retort between the discharge opening 28 and inlet pipe 20 so that the mass or column of material within the retort chamber i1 will descend at a predetermined rate mainly dependent upon the speed of the feeder 52.

The supply system for the solid hydrocarbon feed stock in the arrangement illustrated comprises an overhead track and bucket conveyor 10 discharging into a storage bin H having a regulable discharge through a suitable feeder 12 into the upper end of the pipe 20. The operation of the feeder'12 is advantageously coordinated retort chamber and so, facilitate the maintenance of desirable material and gas flow conditions in the retort chamber.

In accordance with the'invention, an additional gas outlet pip'e is-arranged to open through the top plate l8 above the normal level of the material in the retort chamber I1. The gas outlet pipe 80 has two branches 8| and 82 controlled by valves 83 and 84' respectively. The branch outlet 8| is normally closed except at'starting-up and serves as a heating gas outlet during such pe-v riods. The branch outlet 82 serves as an auxiliary gas outlet for the upper and lower series of outlet ports 35,36 in the mid section of the retort chamber, as is hereinafter described, and leads to associated gas treating apparatus.

A relatively wide range of materials can be used as the circulating solid material serving the dual function of a heat transfermedium and a solid diluent for the hydrocarbon or carbohydrate feed stock, the material chosen depending upon the particular set of operating conditions to be maintained. The material selected for this purpose must be capable of withstanding a rapid rate of temperature change over a substantial temperature range without fracturing or substantial erosion and have a high rate of heat conductivity. Such materials are preferably non-combustible refractories, although a combustible material such as sized pieces of a suitable coke could be used under certain conditions. Preferably however the heat transfer material consists of pellets of ceramic refractory or corrosion resistant alloy or alloy steel, as disclosed in my copending appiication with R. M. Hardgrove, Serial No. 502,580, now Patent No. 2,447,306. The pellets should be of a diameter small enough to minimize thermal shocks and impact stresses and particularly to provide a large amount of heat transfer surface, and yet large enough to withstand the desired gas velocities in the retort chamber without lifting.

In initially starting up apparatus of the character described, the system is filled with pellets of heat transfer material of the character described and the feeding and elevating mechanisms started. All of the gas outlet passages are closed, except the outlet 8|. A fuel gas supply is temporarily introduced into the combustion zone of the retort through the outlet ports 35 and/or 36 and air supplied through the pipe 30 for combustion of the fuel gas. The circulating heat transfer material is heated in this manner sufficiently to bring its temperature at the outlet 28 to 5001000 F. with the heating gases leaving through the gas outlet 8|. The hydrocarbon or carbohydrate feed stock, such as raw bituminous coal crushed so that all of it passes through a medium sized screen, e. g. one-half inch mesh, is then introduced through the inlet pipe 20 along .with the heated pellets from the elevator in the desired volumetric ratio of coal to pellets. As the mixture moves downwardly in the upper part of the chamber, heat is progressively transmitted by radiation and conduction from the heated pellets to the intermingled coal particles. The starting-up gas supply is continued until the desired operating temperatures throughout the retort chamber are reached and is then cut off. The heating gas outlet BI is then closed by the valve 83 and the gas outlets 35, 3B and 82 opened or closed depending upon whether all of the gasewith the operation of the rotary feeder 52 to con- 7 ous end products are to be withdrawn through section oi the retort chamber. The steam supply I! is used first to dilute the air supply and to act as an inert cooling medium for the pellets adjacent the outlet II and later as it iiows upward is used in the water gas reaction.

In normal operation, with the auxiliary outlet I! closed and the series oi outlets I5 and 38 open, the descending intermingled mass of coal and pellets will first move downwardly through the low temperature gasification or distillation zone where the heat transmitted by the pellets will raise the temperature of the coal particles enough to drive out the moisture and the rich low temperature volatile hydrocarbon constituents, which new downwardly through the interstices in the fluent mass to the gas outlets it. The low temperature heating in this zone is suillcient to rapidly fuse the intermingled coal particles into a melted tarry condition and most of the melted coal soon deposits on the surrounding pellets as a tarry layer. The low temperature heating continues for a period suillcient to convert the coal in the descending mass into so-called low-temperature" coke by the time it reaches the upper series of outlets 85. Some higher temperature hydrocarbons are still present in the coke-at this level.

The retort chamber and pellet temperatures sharply increase in the center outlet section of the retort due to the presence therein or high temperature gases from the lower sections. As the mass of coke-coated pellets moves downwardly through this high temperature zone, the

remaining hydrocarbon constituents in the coke are rapidly driven oif. These gaseous hydrocarbons mix with the gases rising from the subj acent retort section and the residence time and high temperatures (1700-2200 F.) to which the gaseous mixture is subjected effects cracking and synthesis of some of the hydrocarbons present to form new'hydrocarbons in a stable or a metastable condition.

In the lower part of the high temperature gasiilcation zone, the descending mass of coke and pellets is contacted by superheated steam at a relatively high temperature and a water gas'reaction takes place between the steam and the coke, forming hydrogen and carbon monoxide which flow upwardly in the retort chamber and mix with the gaseous hydrocarbons driven oil in the superjacent part of the high temperature gasification zone. The steam supply from the pipe 3! is advantageously regulated as close as possible to the theoretical steam requirements for the water gas reaction to thus minimize loss of heat in the outgoing gases.

The heat requirements for the endothermic water gas and pyrolysis reactions and for heating the mass of heat transfer material are supplied substantially entirely by the combustion of the residual carbon remaining on or intermingled with the pellets leaving the water gas reaction zone. The oxygen required for this combustion reaction is supplied by the controlled admission of air through the pipe 30, inlet chamber 26 and screen 24. The air is heated to a high temperature during its passage through the mass of pellets in the lowermost part of the retort chamber, so that when the air encounters the descending carbon coated pellets a rapid combustion of the carbon takes place. The air amino supply is also advantageously maintained sush 8 below the theoretical ongen requirements for complete combustion to minimize the formation of carbon dioxide. The amount of carbon dioxide in the ascending heating gases is further reduced bythe reducing action thereon, COM-0:200, efiected by contact with the descending residual carbon in the superjacent water gas reaction and high temperature gasiilcation zones.

when the gaseous hydrocarbons driven oil in the upper or low temperature gasification zone are withdrawn through the auxiliary outlet II, these end products can be maintained separate from the end products discharging through the outlets 35 and/or and separately treated. Likewise when both sets of outlets II and N are in use, the end products withdrawn therethrough can be separately treated.

The gaseous end products leaving through the outlets 35 and/or It are rapidly quenched to a low temperature by the operation of the gas quenching devices ll in the outlet pipes 42*. This immediate and rapid quenching of the gaseous end products leaving the high temperature zone to a low temperature causes any hydrocarbon end products in a metastable condition when formed to be stabilized for subsequent separation and treatment. The non-condensable gaseous end products are separated in a well known manner and are available for use as a fuel gas for combustion requirements in the plant and for commercial distribution. The condensable products contain a relatively high percentage of constituents suitable for further. treatment to produce aliphatic and aromatic hydrocarbons and other valuable products. A substantial range of regulation of the operating conditions in the retort chamber, and particularly the time and temperatures for the various reactions described, is obtained by controlling the feed stock, air and steam supplies, and varying the rate of movement of the fluent mass of feed stock and heat transfer material downwardly through the retort chamber. The character of the end products can be further controlled by regulating the control valves for the gas outlets 35, 38 and 82 to apportion the gaseous end products between the outlets and vary the treatment in the retort chamber received by the gaseous end products before reaching the respective outlets.

The pellets leave the combustion zone with substantially all of their residual carbon coating completely consumed and move downwardly with the ash residue to the outlet openings 25 and 28. The pellet temperature is reduced to the desired outlet temperature by contact with the steam and air flowing upwardly to the water gas reaction and combustion zones. A pellet temperature of 500-1000 F. is normally desired at the outlet 28 to provide sufllcient residual heat in the pellets for the low temperature gasification of the entering coal when the pellets are returned to the upper end of the retort chamber. The ash residue and any other fines present in the material discharged are preferably separated in a suitable manner, such as by a steam blast from a steam pipe entering a stepped bottom section SI of the pipe 49 at a point above the rotary feeder 52 and sweeping through the moving mass of material in that location. The steam and separated fines are discharged to a suitable receiver (not shown) through a screened outlet pipe 02 in the opposite side of the pipe 40.

The location of the series of gas outlets and 36 at the mid-section of the retort chamber is especially advantageous -rom an operating standpoint as it permits the immediate withdrawal and quenching of the valuable metastable hydrocarbon formed in the high temperature section of the retort chamber. A further advantage of this location is the substantially lower gas quantities and resultant low gas velocity conditions in the low temperature gasification zone, providing a low pressure drop in this section. This low pressure drop not only reduces the power requirements of the apparatus, but also minimizes lifting and carryover of the fines in the upper section of the retort chamber. With a feed stock of solid hydrocarbon or carbohydrate material, loss of fines therein due to carryover with the gases would correspondingly reduce the ,efliciency of the process, but with the described gas outlet arrangement such losses are avoided. Another advantage is the resultant confining of the low temperature gasification to the heating effect of the heat transfer material in that section, avoiding the use of products of combustion from the lower sections of the retort chamber.

tion are consequently undiluted with such products of combustion.

I claim:

1. A process of heat treating coal as a feed stock which comprises passing a mixture of the feed stock and a heated solid heat transfer material in a porous fluent mass downwardly through a retort chamber, maintaining heat transfer contact between the feed stock and said heat transfer material for a period sufficient to effect a, low temperature gasification of the feed stock in a zone at the upper part of said mass, then passing the mixed mass of remaining feed stock and heat transfer material through a subjacent high temperature zone for further heat treatment, supp-lying combustion air to the lower part of said chamber for burning the feed stock residual carbon in said mass in a subjacent zone below said high temperature zone to supply the heat requirements of the process, returning the heat transfer material to the low temperature gasification zone with a heat content suflicient to effect said low temperature gasification, and withdrawing gaseous end products directly from the high temperature heating zone of said chamher.

2. A process of continuously heat treating a carbon containing feed stock which comprises introducing the feed stock into the upper part of a vertically elongated retort chamber in commingled relation with heated pieces of heat transfer material to form a continuous porous fluent mass in said chamber, moving said porous fluent mass of feed stock and heat transfer material substantially continuously downwardly through said chamber, effecting a low temperature gasification of the feed stock while in a zone at the upper part of said mass by a heating effect mainly due to heat transfer from said heat transfer material, subjecting a lower portion of the descending feed stock to a high temperature gasification effect, supplying combustion air to the lower part of said chamber for burning the descending feed stock residue in said mass while in a subjacent section of said chamber below said high temperature gasification zone to supply the heat required in said gasification effect, recovering the reaction products from said low and high temperature gasification zones, and returning The low temperature hydrocarbons driven off in this sec-.

10 heat transfer material to the upper part of the chamber at a temperature suflicient to effect said low temperature gasification. 3. A process of continuously heat treating coa as feed stock which comprises introducing the feed stock into the upper part of a vertically elongated retort chamber in commingled relation with heated pieces of non-combustible heat transfer material to form a continuous porous fluent mass in said chamber, moving said porous fluent mass of feed stock and heat transfer material downwardly through successive subjacent low and high temperature gasification zones and a combustion zone, effecting a, low temperature gasification of the feed stock in said low temperature gasification zone by a heating effect substantiallysolely due to heat transfer from said heat transfer material, then subjecting the descending feed stock to a high temperature gasiflcation effect at a position intermediate the height of said mass, supplying combustion air to the lower part of said chamber for burning the descending feed stock residue in said mass in which comprises introducing the feed stock into the upper part of a vertically elongated retort chamber in commingled relation with heated pieces of heat transfer material to form a' continuous porous fluent mass descending in said chamber, effecting -a low temperature gasification of the feed stock in the upper part of said mass by a heating effect sufiicient to convert the feed stock into a low temperature coke or char, subjecting the descending feed stock in a subjacent portion of said mass to a high temperature gasification effect sufficient to drive off the remaining hydrocarbon constituents, passing steam in contact with the descending feed stock in a section of said mass below said high temperature gasification zone for the generation of water gas,

supplying combustion air to the lower part of said chamber for burning the descending feed stock residue in said mass to generate the heat required in said gasification and water gas generating zones, withdrawing the gases generated in the high temperature gasification and water gas reaction zones from said chamber at said high temperature gasification zone, and continuously returning the heat transfer material from the last of said reaction zones to the first at a temperature sufficient to effect said low temperature gasification.

5. A process of heat treating coal as feed stock which comprises introducing the feed stock into the upper part of a vertically elongated retort chamber in commingled relation with heated pieces of heat transfer material to form a continuous porous fluent mass descending in said chamber, effecting a low temperature gasification of the feed stock in the upper part of said chamber by heat transfer to the feed stock from the heat transfer material, subjecting the descending feed stock in a subjacent portion of said chamber to a high temperature heating effect suflicient to drive off remaining volatile constituents and effect the formation of hydrocarbons in a metastable condition, passing steam in contact with the descending feed stock residue in a subjacent section of said chamber for the generation of water gas, burning the descending feed stock residue in said mass with preheated oxygen in a subiacent section of said chamber below said water gas reaction zone to generate the heat required in said gasiiication and water gas reaction zones, withdrawing the gases generated in the high temperature gasification and water gas reaction zones from the chamber at the upper part of said high temperature gasincation zone, rapidly quenching the gaseous end products withdrawn to stabilize any hydrocarbons in a metastable condition, and continuously returning the heat transfer material from the last ofsaid reaction zones to the first at a temperature sufficient to effect said low temperature gasiflcation.

6. A process of continuously heat treating a carbon containing feed stock which comprises introducing the feed stock into the upper part of a vertically elongated retort chamber in commingled relation with heated pieces of non-combustible heat transfer material to form a continuous porous fluent mass descending in said chamber, eifecting a low temperature gasification of the feed stock while in th upper part of said chamber by a-heating effect mainly due to heat transfer fromsaid heattransfer material suilicient to convert the feed stock into a low temperature coke or char, subjecting the descending feed stock while in a subjacent and intermediate portion of said chamber to a high temperature gasiflcation effect sufilcient to drive oil. the remaining volatile constituents, supplying superheated steam in intimate contact with the descending feed stock residue whil in a section of said chamber below said high temperature zone for the generation of water gas, supplying comb tion air to the lower part of said chamber or burning the remaining feed stock residue in said mass to generate the heat required in said gasiiication and water gas generating zones, withdrawing the gases'generated in the high temperature gasiflcation and water gas reaction zones from the chamber at a point in said high temperature gasiflcation zone, alisorbing heat from the descending heat transfer material while in the portion of the retort chamber below the combustion zone to superheat steam, and returning the heat transfer material to the upper part of the chamber with a heat content suilicient to effect said low temperature sasiiication.

7. A process of continuously heat treating a carbon containing feed stock which comprises introducing the feed stock into the upper part of a vertically elongated retort chamber in commingled relation with heated pieces of heat transfer material to form a continuous porous fluent mass descending in said chamber, eff cting a low temperature gasiflcation of the feed stock while in the upper part of said chamber by a heating effect substantially solely due to heat transfer from said heat transfer material and suillcient to convert the feed stock into a low temperature coke or char, subjecting the descending feed stock 9 while in a subiacent portion of said chamber to a high temperature gasiiication effect sufficient to drive off the remaining volatile constituents,

subjacent section of said chamber for the generation of water gas, burning the remaining feed stock residue in said mass with preheated combustion air to generate the heat required in said gasification and water gas generating zones, withdrawing the gases generated in the high temperature gasification and water gas reaction zones from the upper part of said high temperature gasiflcation zone, absorbing heat from the descending heat transfer material while in the portion of the retort chamber below the combustion zone to preheat combustion air and superheat steam, and returning the heat transfer material to the upper part of the chamber with a heat content sufllcient to effect said low temperature gasiflcation.

8. A process of gasifying a coal feed stock which comprises passing a mixture of crushed solid feed stock and a heated solid non-combustible heat transfer material in a volumetric ratio providing a porous fluent mass down.- wardly through a retort chamber, maintaining heat transfer contact between the feed stock and the heat transfer material sufficient to effect gasification of the feed stock to a low temperature coke, then passing the mass through a subjacent high temperature gasiflcation zone maintained at a temperature about 1500 Fr to'gasify the remaining volatile constituents, passing steam into contact with the feed stock residual carbon to effect a water gas reaction, supplying conbustion air to the lower part of said chamber for burning the remaining feed stock residual carbon in the lower part of said chamber, returning heat transfer material to the low temperature gasiilcation zone with a heat content sufficient to effect said low temperature gasiiication, withdrawing the gaseous end products from said chamber at a high temperature level therein, and rapidly quenching the gaseous and products as withdrawn to stabilize any hydrocarbons in a metastable condition therein.

ERVIN G. BAILEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,450,327 Meischke-Smith Apr. 3, 1923 1,568,018 Forrest et a1. Dec. 29, 1925 1,699,989 Pyzel Jan. 22, 1929 1,714,453 Schwarz May 21, 1929 2,323,501 Tuttle July 6, 1943 2,348,699 Tuttle May 9, 1944 2,351,214 Kaufmann et al. June 13, 1944 2,398,954 Odell Apr. 23, 1946 OTHER REFERENCES Griswold: Fuels and Their Combustion," 1946, McGraw-Hill Book 00., New York, page 226. 

1. A PROCESS OF A HEAT TREATING COAL AS A FEED STOCK WHICH COMPRISES PASSING A MIXTURE OF THE FEED STOCK AND A HEATED SOLID HEAT TRANSFER MATERIAL IN A POROUS FLUENT MASS DOWNWARDLY THROUGH A RETORT CHAMBER, MAINTAINING HEAT TRANSFER CONTACT BETWEEN THE FEED STOCK AND SAID HEAT TRANSFER MATERIAL FOR A PERIOD SUFFICIENT TO EFFECT A LOW TEMPERATURE GASIFICATION OF THE FEED STOCK IN A ZONE AT THE UPPER PART OF SAID MASS, THEN PASSING THE MIXED MASS OF REMAINING FEED STOCK AND HEAT TRANSFER MATERIAL THROUGH A SUBJACENT HIGH TEMPERATUE ZONE FOR FURTHER HEAT TREATMENT, SUPPLYING COMBUSTION AIR TO THE LOWER PART OF SAID CHAMBER FOR BURNING THE FEED STOCK RESIDUAL CARBON IN SAID MASS IN A SUBJACENT ZONE BELOW SAID HIGH TEMPEATURE ZONE TO SUPPLY THE HEAT REQUIREMENTS OF THE PROCESS, RETURNING THE HEAT TRANSFER MATERIAL TO THE LOW TEMPERATURE GASIFICATION ZONE WITH A HEAT CONTENT SUFFICIENT TO EFFECT SAID LOW TEMPERATURE GASIFICATION, AND WITHDRAWING GASEOUS END PRODUCTS DIRECTLY FROM THE HIGH TEMPERATURE HEATING ZONE OF SAID CHAMBER. 